#include <bits/stdc++.h>
using namespace std;

class Solution {
    int m, n, count = 0;
    int dx[4] = {0, 0, -1, 1};
    int dy[4] = {-1, 1, 0, 0};

public:
    int numIslands(vector<vector<char>>& grid) {
        m = grid.size(), n = grid[0].size();
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (grid[i][j] == '1') {
                    dfs(grid, i, j);
                    count++;
                }
            }
        }
        return count;
    }
    void dfs(vector<vector<char>>& grid, int i, int j) {
        grid[i][j] = '0';
        for (int k = 0; k < 4; k++) {
            int x = dx[k] + i;
            int y = dy[k] + j;
            if (x >= 0 && x < m && y >= 0 && y < n && grid[x][y] == '1') {
                dfs(grid, x, y);
            }
        }
    }
};